Splined idler for scallop resistance

ABSTRACT

An idler wheel for use with a track chain of a vehicle that includes a plurality of track pins and bushings comprises a main body that includes a generally cylindrical configuration defining an axis of rotation, a circumferential direction and a radial direction, the main body including a central portion disposed along the axis of rotation defining an axial extremity of the radial portion, and at least a first outside portion disposed along the axis of rotation that includes an undulating circumferential perimeter.

CROSS-REFERENCE TO RELATED APPLICATION

This continuation application claims the benefit of U.S. patentapplication Ser. No. 15/253,363 filed on Aug. 31, 2016, entitled“Splined Idler for Scallop Resistance”, the contents of which is herebyincorporated by reference in its entirety.

TECHNICAL FIELD

The present disclosure relates to an idler wheel that is used as a partof a track chain assembly attached to the undercarriage of track-typevehicles used for off-road operations such as those that use endlesstracks for moving on the ground. Specifically, the present disclosurerelates to an idler wheel that is configured to reduce the scalloping oftrack links that may lead to track chain and machine maintenance.

BACKGROUND

In many current applications, track links that are part of track chainsdevelop a scallop pattern on their top or rail surfaces that contactvarious drive and support members of the undercarriage including rollersand idler wheels. The scallops look like depressions on the rail surfaceof the links. These depressions are caused by contact of the rollers andthe idler in a consistent place on the link as the track chaincontinuously revolves around on the drive sprocket, idler wheels and therollers. In many cases, the track links have rails with a center portionthat is thicker in a direction parallel to the axis of rotation of theidler wheel as compared to a similar thickness of the end portions.Consequently, an idler wheel and roller tend to contact the centerportion more completely and less completely at the ends where thatportion of the link is not overlapped by an adjacent link. This leads adeeper more complete scallop, often referred to as a primary scallop,being formed at the center of the rail portion of the track link, whilea secondary scallop that this less complete may be formed at the endportions of the rail of the track link. These secondary scallops areoften positioned at the ¼ position of the rail, measured from the frontof the rail, and at the ¾ position of the rail, also measured from thefront of the rail, while the primary scallop would be located betweenthe ¼ and ¾ positions.

Scalloped track links may lead to various problems. For example, overtime, the manner in which the idler wheel and rollers contact the linksmay become uneven, causing vibration that may lead to an uncomfortableride. Also, this may lead to maintenance issues for the undercarriageand the machine.

SUMMARY

An undercarriage for use with a vehicle that includes an endless trackdrive is provided. The undercarriage comprises a track chain including aplurality of track pins and track bushings disposed about the trackpins, and a plurality of track links that are connected to each other byeither a track pin or a track bushing, wherein at least one track linkcomprises defines a plurality of apertures for receiving a track pin orbushing. The undercarriage may further comprise an idler wheel includinga main body that includes a generally cylindrical configuration definingan axis of rotation, a circumferential direction and a radial direction,the main body including a central portion disposed along the axis ofrotation defining a radial extremity of the central portion, and atleast a first outside portion disposed along the axis of rotation thatincludes an undulating circumferential perimeter with a plurality ofapexes and valleys. The undulating circumferential perimeter may beexposed and configured to contact the plurality of track links of thetrack chain tangentially without contacting one of the plurality oftrack bushings.

A machine comprising an undercarriage is provided. The undercarriage maycomprise a track chain including a plurality of track pins and trackbushings disposed about the track pins, and a plurality of track linksthat are connected to each other by either a track pin or a trackbushing, wherein at least one track link comprises defines a pluralityof apertures for receiving a track pin or bushing. The undercarriage mayfurther comprise an idler wheel including a main body that includes agenerally cylindrical configuration defining an axis of rotation, acircumferential direction and a radial direction, the main bodyincluding a central portion disposed along the axis of rotation defininga radial extremity of the central portion, and at least a first outsideportion disposed along the axis of rotation that includes an undulatingcircumferential perimeter with a plurality of apexes and valleys. Theundulating circumferential perimeter may be exposed and configured tocontact the plurality of track links of the track chain tangentiallywithout contacting one of the plurality of track bushings.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are incorporated in and constitute apart of this specification, illustrate several embodiments of thedisclosure and together with the description, serve to explain theprinciples of the disclosure. In the drawings:

FIG. 1 is a side enlarged view of an idler wheel according to anembodiment of the present disclosure used with a track chain assembly aspart of a machine undercarriage.

FIG. 2 is a side view of the idler wheel of FIG. 1 shown in isolationfrom the machine undercarriage.

FIG. 3 is a perspective view of the idler wheel of FIG. 2 shown inpartial cross-section to show various components of the rotatingconnection of the idler wheel to the axle.

FIG. 4 is a front view of a track chain assembly and idler wheelaccording to an embodiment of the present disclosure, showing how theidler wheel contacts the top rails of the track links.

FIG. 5 is a simplified schematic view of another embodiment of an idlerwheel according to the present disclosure.

FIG. 6 is an enlarged front view of an idler wheel according to anembodiment of the present disclosure to show more clearly the dimensionsof the undulations that may be employed.

FIG. 7 is a side view of a tractor using an endless track chain that mayuse an idler wheel in accordance with various embodiments of the presentdisclosure.

FIG. 8 is a side view of an endless track that is similar to thatdisclosed in FIG. 7 but is isolated from the tractor, illustrating moreclearly an in-line configuration of endless track.

FIG. 9 is a front view of an endless track similar to that shown in FIG.8 except that is uses an elevated drive sprocket.

FIG. 10 is an enlarged front view of a pair of track links that arejoined together by a track pin and bushing in a manner that is similarto the tracks illustrated in FIGS. 8 and 9.

FIG. 11 is a top view of the track links, bushing and track pin of FIG.10. The track shoes are removed for extra clarity.

FIG. 12 is a perspective sectional view of track links, a bushing andtrack pin that is similar to that shown in FIG. 11.

FIG. 13 is a plan sectional view of track links, bushing and track pinsimilar to that shown in FIG. 12, where the track pin is of solidconstruction, lacking a central oil groove that runs along itscylindrical axis.

DETAILED DESCRIPTION

Reference will now be made in detail to embodiments of the disclosure,examples of which are illustrated in the accompanying drawings. Whereverpossible, the same reference numbers will be used throughout thedrawings to refer to the same or like parts. In some cases, a referencenumber will be indicated in this specification and the drawings willshow the reference number followed by a letter for example, 100 a, 100 betc. It is to be understood that the use of letters immediately after areference number indicates that these features are similarly shaped andhave similar function as is often the case when geometry is mirroredabout a plane of symmetry. For ease of explanation in thisspecification, letters will often not be included herein but may beshown in the drawings to indicate duplications of features discussedwithin this written specification.

Various embodiments of the present disclosure include an idler wheelthat is configured to reduce the scalloping of track links. This may beaccomplished in a number of ways such as by providing an undulatingcontact surface on the idler wheel that contacts the track link in adifferent position most the time the idler wheel contacts thatparticular track link. To this end, the idler wheel may have anundulating profile that is consistent or varying about thecircumferential perimeter of the idler wheel, that has an odd number ofcontacting portions about the circumference of the idler wheel, and/orthe effective tangential circular distance about the circumference ofthe undulating profile may not be evenly divisible into the linearlength of the track chain that the idler wheel is intended to contact,etc.

FIGS. 1 thru 3 illustrate an embodiment of an idler wheel 200 andundercarriage system 300 according to the present disclosure. Theundercarriage system 300 of FIGS. 1 and 3 is directed to a track chainassembly 302 using a plurality of straight track links 304, so called,as its cross-sectional area does not vary from one end to the other. Itis to be understood that the configuration of the track link for anyembodiment discussed herein may be varied as needed or desired. Anyembodiment of a track link described herein may be used as part of atrack chain assembly of a vehicle 100 that includes a plurality of trackpins and bushings. This will be described in further detail laterherein.

Starting with FIGS. 1 and 3, an undercarriage 300 for use with a vehiclethat includes an endless track drive is shown. The undercarriage 300comprises a track chain assembly 302 including a plurality of track pins306 and track bushings 308 disposed about the track pins 306, and aplurality of track links 304 that are connected to each other by eithera track pin 306 or a track bushing 308, wherein at least one track link304 comprises defines a plurality of apertures for receiving a track pinor bushing.

Looking at FIGS. 1-3, a rear idler wheel 200 is also shown that includesa main body 202 that includes a generally cylindrical configurationdefining an axis of rotation A, a circumferential direction C and aradial direction R. The main body 202 includes a central portion 204disposed along the axis of rotation A defining radial extremity 206 ofthe central portion 204, and at least a first outside portion 208disposed along the axis of rotation A that includes an undulatingcircumferential perimeter 210. The radial extremity 206 of the centralportion 204 may nor may not be configured to make contact with thebushings 308 of the track chain assembly 302.

In addition to the idler wheel 200 being shown to have a rotatingattachment to the frame 314 of the undercarriage 300, a support roller310 and a drive sprocket 312 are also shown to have rotating attachmentsto the frame 314, represented by rotation axes A and B respectively inFIG. 1. As also shown in FIG. 1, an elevated configuration (drivesprocket is elevated) of an undercarriage system 300 is shown but it iscontemplated that other embodiments could use an inline configuration aswill be described later herein.

For this embodiment as shown in FIGS. 2 and 3, the undulatingcircumferential perimeter 210 defines a radial extremity 212 of thefirst outside portion 208 of the idler wheel 200, wherein the radialextremity 206 of the central portion 204 is further away from the axisof rotation A than the radial extremity 212 of the first outside portion208 along the radial direction R. This may not be the case in otherembodiments. Similarly, the central portion 204 may include an axialoffset (not shown in FIGS. 2 and 3) near its radial extremity 206 butthis may not be the case in other embodiments.

FIG. 2 shows a hub 216 that may be used to attach the idler wheel 200 tothe axle of the machine. The axle 214 and other parts of the idler wheelassembly 200 are shown in FIG. 3. The axle 214 is surrounded by bearings232. Rotating face seals 234 are also employed as is known in the art tohold lubrication such as oil in the rotating joint. The rim portion 236of the idler wheel assembly 200 is connected to the hub 216 via a pairof annular shaped plates 238 that are supported and interconnected byspoke members 240 contained within the idler wheel assembly 200. Idlerwheels of other configurations including having unitary construction arealso contemplated to be within the scope of the present disclosure.

As can be seen best in FIG. 3, the main body 202 includes a secondoutside portion 208′ that is positioned on the axially opposite side ofthe central portion 204 compared to the first outside portion 208,wherein the second outside portion 208′ is similarly configured as thefirst outside portion 208. For this embodiment, the idler wheel 200 issymmetrical about an axial plane AP centered on the axis of rotation Aof the idler wheel 200 (see FIG. 4). Other embodiments may beasymmetrical.

As best seen in FIG. 2, the undulating circumferential perimeter 210 ofthe idler wheel 200 includes a plurality of apexes 218 and valleys 220.An apex or valley is that portion of the perimeter 210 where theinflection of the perimeter changes, that is to say, a tangent to theperimeter changes its slope from a positive slope to a negative slope,or vice versa. A curve 222 may be defined about the circumferentialperimeter 210 of the first outer 208 portion that is tangent to everyapex 218 of the undulating circumferential perimeter 210. As shown, thecurve 222 is a circle but this may not be true for other embodiments.

As best understood by referring to FIGS. 1, 2, and 7-9, the track chainassembly 302 defines a track chain length L302 and the circle 222defines a circumferential length L222, and the track chain length L302divided by the circumferential length L222 of the circle yields anon-integer value in some embodiments. This helps to ensure that theapex 218 of the undulating perimeter 210 will contact a different spotmost the time the idler wheel 200 contacts a particular link 304. Thishelps reduce the likelihood of scalloping the link 304.

Focusing now on FIG. 2, each curve segment 224 of the undulatingperimeter 210 includes an arcuate shape. It is contemplated that in someembodiments that the curve segment 224 could be a concavely shapedradius, as would be the case for a valley 220, and a convexly shapedradius, as would be the case for an apex 218. These radii couldtransition from one to the other directly, or indirectly, as would bethe case if a straight or flat curve joined them together. Any suitableundulating perimeter may be used in other embodiments includingzig-zagged with rounded peaks, squared with rounded corners, sinusoidal,polynomial such as a spline, involute, etc.

In yet other embodiments, the undulating circumferential perimeter 210may include an odd number of apexes 218 that helps to ensure that anapex 218 contacts a different portion of a particular track link 304most the time as the track link 304 revolves around the undercarriage300 and contacts the idler wheel 200 once more. Also, as best seen inFIG. 6, the linear circumferential distance L218 from one apex 218 tothe next apex 218′ may be the same about the entire circumferentialperimeter 210 of the first outer portion 208 of the idler wheel 200. Insuch a case or in other embodiments, the undulating circumferentialperimeter 210 may comprise a circular array 226 of repeating geometricalapexes 218 and valleys 220 about the axis of rotation A. Thisconsistency may not be present in other embodiments. The dimensions ofthe undulating perimeter 210 may be approximately measured like asinusoidal waveform or the like, having a radial amplitude RA and a halfwavelength HW. It is contemplated that the amplitude RA may range from5-10 mm and that the half wavelength HW may range from 10-160 mm invarious embodiments.

FIG. 4 depicts another version of the idler wheel 200′ with outsideflanges 242. As shown, the idler wheel 200′ contacts the rails 316 ofthe track links 304. For this embodiment, the flanges 242 are positionedclosely to the outside of the rails 316 of the links 304, helping toprevent lateral movement of the track chain assembly 302 with respect tothe idler wheel 200′. The central portion 204 of the idler wheel 200′does not contact the bushing 308 and the outer portions of the idlerwheel 200 have undulating circumferential perimeters 210 in a mannerconsistent with what has been described with reference to FIGS. 1-3.

Looking at FIG. 5, the plurality of track links 304 may include a railportion 316 that is configured to complimentarily mate with thecircumferentially undulating perimeter 210′ of the idler wheel 200″.This may involve the provision of an undulating surface 318 on the railportion 316 of the link 304. For the embodiment depicted in FIG. 5, theundulating circumferential perimeter 210′ is interrupted along thecircumferential direction C of the idler wheel 200′. That is to say,there are gaps 228 between the undulations. Each portion of the idlerwheel 200′ that forms an apex 218 may be referred to as a spline 230. Asshown in FIGS. 1 and 2, the undulations may be continuous oruninterrupted in other embodiments. The rail surface of other tracklinks may be flat as illustrated in FIGS. 1 and 4.

INDUSTRIAL APPLICABILITY

In practice, a track chain assembly and/or an idler wheel may be sold,manufactured, bought etc. and attached to the machine in the aftermarketor original equipment scenarios. That is to say, the machine may be soldwith the track chain assembly and idler wheel according to embodimentsdescribed herein or the machine may be retrofitted, repaired,refurbished to use any of the embodiments discussed herein. The idlerwheel may be machined from a single piece of material to provide asuitable undulating profile that is intended to contact the links of thetrack chain assembly or the idler wheel may include an assembly ofmultiple components. In other embodiments, the splines may be added tothe idler wheel by fastening, welding, etc. Continuous undulatingprofiles may also be added as one piece or in segments to an idlerwheel, etc.

FIG. 7 illustrates a track-type tractor 100 employing a pair of endlesstrack chain assemblies 102 (one shown) of this invention thereon.Although the track assembly is particularly adapted for use on atractor, it should be understood that the track assembly will findapplication to other vehicles, such as track-type excavators or anyother type of off-road vehicle or machinery. In the tractor applicationillustrated in FIG. 7, each track chain assembly 102 is mounted in aconventional manner on a drive sprocket 104, an idler 106, a pluralityof longitudinally spaced track rollers 108, and a pair of upper guide orcarrier rollers 110, when needed. The idler wheel may be substitutedwith idler wheel 200, 200′, etc. as described earlier herein. Also, thelinks of the track chain assembly 102 of FIG. 7 are shown to be offsetlinks instead of straight links as shown in FIG. 1.

Referring to FIGS. 8 and 9, a track assembly 102 comprises a pluralityof track shoes 112 which are pivotally interconnected by an articulatedlink assembly 114. Link assembly 114 is disposed intermediate the widthsof track shoes 112 and includes a plurality of pairs of links, pivotallyinterconnected together by standard pin and bushing assemblies 118. Theteeth 120 of drive sprocket 104 engage the bushings of pin and bushingassemblies 118 to drive track assembly 102 in a conventional manner withthe track assemblies being guided by idler 106 and rollers 108 and 110which engage upper rail portions of links. The main difference betweenthe configurations of the track assembly of FIGS. 8 and 9 is that FIG. 8is an inline configuration, so called as the drive sprocket is in-linewith the front idler wheel forming a substantially ovular path for thetrack, while FIG. 9 shows an elevated configuration, so called as thedrive sprocket is vertically above the lower idler wheels forming asubstantially triangular path for the track. Again, idler wheels 106 inFIGS. 8 and 9 may be substituted with idler wheels 200, 200′, 200″ etc.as described earlier herein.

With continued reference to FIGS. 8 and 9, the lower rollers are oftencalled track rollers 108 as they support the weight of the vehicle andtransfer it to the track and then to the ground while the upper rollersare often called carrier rollers 110 as they only carry or support thetrack, limiting or sometimes modifying the catenary hang of the track.The drive sprockets 104 have segments 122 with drive teeth 120 connectedto them or integrally formed therewith that mesh with the links in thetrack chain assembly 102, powering movement of the track, and thus thevehicle. The shoes 112 include provide movable platforms that engage theground and include ribs or grousers 124 that penetrate the ground,providing traction. The idler wheels 106 lack teeth but ride between thelinks (see G in FIG. 5) and on top of the rails of the links, limitingside to side movement of the track. Similarly, the rollers 108, 110provide a conduit for the transfer of weight, and in many cases, providea way to adjust the tension in the track. The rollers 108, 110 also ridebetween the links 116 and on top of the rails of the links, limitingside to side movement of the track.

Turning now to FIGS. 10 and 11, they show an example of a link assembly114 that includes a pair of track links that are joined together by atrack pin and bushing assembly 118 in a manner consistent with thetracks illustrated in FIGS. 8 and 9. The track pin and bushing assembly118 form a joint that includes a cylindrical pin 126, and a rotatabletubular bushing 128. The pin 126 has opposite end portions 132 (bestseen in FIG. 11), each of which is pressed and non-rotatably mountedinto a respective one of the bores 134 formed by a protruding boss 136of the outboard end collars 138 of each link 116 in a link set 114. Thepin and bushing assembly 118 further includes a method and device formechanically interlocking the pin 126 within such bores 134 to preventany axial movement of the links 116 along a longitudinal or cylindricalaxis 140 of the pin 126.

Other types of methods for mechanically interlocking the pin to thelinks that are known or that will be devised in the art may be employed.One mechanically interlocking method comprises a circumferentiallydisposed, generally arcuately shaped groove formed about each of the endportions of the pin and at least one mechanically formed nodule whichprotrudes radially inwardly from each of the bores into a respective oneof the grooves. The mechanically formed nodules are preferably formed byusing a punch device. Preferably, a pair of such punch devices arelocated perpendicular to the pin axis on each of the flats provided onthe pin boss. The application of a sufficient force of the punch deviceswill result in the extrusion of the boss metal into the groove. Othermethods for achieving this are also available and may be used.

Referring to FIG. 12, there is shown a portion of an undercarriage for atrack-type machine that uses a track chain assembly 102 and linkassembly 114 that are similar to those described thus far herein. Thetubular bushing 128 is provided with a pin bore 142 which is of a sizesufficient to freely rotatably mount the bushing 128 about the pin 126.Bushing 128 has a pair of opposite end faces 144 and is of a size toextend between and to freely rotatable relative to the inboard endcollars 146.

As shown in FIG. 12, each link assembly includes inboard links andoutboard links. Inboard links and outboard links may be coupled togetherwith a plurality of additional inboard and outboard links (not shown),to form an endless chain extending about a conventional drive mechanismincluding one or more track idlers and a drive sprocket. This may beused in a variety of track-type machines, such as a track-type tractor,tracked excavator, tracked loader, or the like. One practicalimplementation of the teachings set forth herein is contemplated to bein track-type tractors used in particularly harsh field conditions, suchas mines and landfills.

The track pin 126 may be press fit with outboard links. In oneembodiment, retention rings 148 or some other mechanism for positive pinretention may be coupled with pin 126 to enhance the strength of thecoupling with outboard links 200, 200′. In the embodiment shown, inboardlinks and outboard links include S-shaped or offset links, however thepresent disclosure is not limited in this regard and straight link trackmight also be used. During operation as already discussed, one or moretrack idlers and a drive sprocket may engage with the bushing 128 toguide and provide power to the track in a conventional manner. As willbe familiar to those skilled in the art, some structure for lubricatingsurfaces which move against one another within the track assembly may bedesirable. To this end, the pin 126 may include an oil passage 150 whichserves as an oil reservoir for supplying oil to desired locations withintrack segment.

During track assembly at the factory or during track repair orservicing, lubricating oil may be supplied into passage 150, and the oilpassage may be plugged to seal the lubricating oil therein. A set ofseals 152 may also be provided, which fluidly seal between outboardlinks and bushing 128 to retain oil within the link assembly 114. Thelink assembly 114 also includes a set of thrust rings 154, eachpositioned between the bushing 128 and one of outboard links 116′.Thrust rings 154 can react to thrust loads through the link assembly 114and may be configured to prevent compressive forces on seals 152 whichcan otherwise impart a tendency for seals to fail. Each of thrust rings154 may be uniquely configured to provide a robust mechanism forreacting thrust loads, but also facilitate the transfer into andmaintaining of oil within a region of the link assembly 114 definedbetween bushing 128 and outboard links, and also between each seal 152and the pin 126. It should be noted that the oil passage is shown indotted lines, indicating that in certain embodiments, it may not bepresent, such as will now be described.

FIG. 13 shows another track link assembly 114 that is known in the artthat lacks an oil passage or other void that surrounds the longitudinalaxis of the pin. This link assembly 114 includes a seal assembly 156that includes first and second seal members 158, 160 that providesealing between the inboard end collars 146 of the outboard link and thebushing 128. Each of the seal assembly 156 is disposed within each ofthe counterbores 162 between the shoulder 164 of the counterbore and theadjacent outer end face 144 of the bushing 128 and in sealing engagementagainst the outer end face 144. These type of seals are often referredto as rotating face seals as they allow the bushing to rotate relativeto the pin 126 and outboard link while still keeping lubrication fromleaking. Also, thrust rings are provided between the pin and sealassembly for reasons already explained above. The pin includes regionsthat absorb loads from the links either directly or indirectly throughthe bushing. Specifically, region 166 is in contact with the outboardlink 116′ while region 168 is in contact with the bushing 128 directlyunderneath the inboard link.

It will be apparent to those skilled in the art that variousmodifications and variations can be made to the embodiments of theapparatus and methods of assembly as discussed herein without departingfrom the scope or spirit of the invention(s). Other embodiments of thisdisclosure will be apparent to those skilled in the art fromconsideration of the specification and practice of the variousembodiments disclosed herein. For example, some of the equipment may beconstructed and function differently than what has been described hereinand certain steps of any method may be omitted, performed in an orderthat is different than what has been specifically mentioned or in somecases performed simultaneously or in sub-steps. Furthermore, variationsor modifications to certain aspects or features of various embodimentsmay be made to create further embodiments and features and aspects ofvarious embodiments may be added to or substituted for other features oraspects of other embodiments in order to provide still furtherembodiments.

Accordingly, it is intended that the specification and examples beconsidered as exemplary only, with a true scope and spirit of theinvention(s) being indicated by the following claims and theirequivalents.

What is claimed is:
 1. An undercarriage for use with a vehicle that includes an endless track drive, the undercarriage comprising: a track chain including a plurality of track pins and track bushings disposed about the track pins; and a plurality of track links that are connected to each other by either one of the plurality of track pins or a track bushings, wherein at least one of the plurality of track links defines a plurality of apertures for receiving one of the plurality of track pins or bushings; and an idler wheel including a main body that includes a generally cylindrical configuration defining an axis of rotation, a circumferential direction and a radial direction, the main body including a central portion disposed along the axis of rotation defining a radial extremity of the central portion; and at least a first outside portion disposed along the axis of rotation that includes an undulating circumferential perimeter including a plurality of apexes and valleys, wherein the undulating circumferential perimeter is exposed and configured to contact the plurality of track links of the track chain tangentially while also being spaced away from each of the plurality of track bushings.
 2. The undercarriage of claim 1 wherein the undulating circumferential perimeter defines a radial extremity of the first outside portion of the idler wheel, wherein the radial extremity of the central portion is further away from the axis of rotation than the radial extremity of the first outside portion.
 3. The undercarriage of claim 1 wherein the main body portion includes a second outside portion that is positioned on the axially opposite side of the central portion compared to the first outside portion, wherein the second outside portion is similarly configured as the first outside portion.
 4. The undercarriage of claim 3 wherein the main body of the idler wheel defines an axial plane centered on the axis of rotation of the idler wheel and the idler wheel is symmetrical about the axial plane.
 5. The undercarriage of claim 1 wherein the undulating circumferential perimeter includes a plurality of apexes and valleys, and wherein a curve may be defined about the circumferential perimeter of the first outside portion that is tangent to every apex of the undulating circumferential perimeter.
 6. The undercarriage of claim 5 wherein the curve is a circle.
 7. The undercarriage of claim 6 wherein the track chain defines a track chain length and the circle defines a circumferential length, and wherein the track chain length divided by the circumferential length of the circle yields a non-integer value.
 8. The undercarriage of claim 5 wherein the undulating circumferential perimeter includes a plurality of curve segments, wherein each curve segment includes an arcuate shape.
 9. The undercarriage of claim 5 wherein the undulating circumferential perimeter includes an odd number of apexes.
 10. The undercarriage of claim 1 wherein the plurality of apexes and valleys includes one apex that is circumferentially adjacent to the next apex and the linear circumferential distance from one apex to the next apex is the same about the entire circumferential perimeter of the first outside portion of the idler wheel.
 11. The undercarriage of claim 10 wherein the undulating circumferential perimeter comprises a circular array of repeating geometrical apexes and valley about the axis of rotation.
 12. The undercarriage of claim 11 wherein the undulating perimeter includes a sinusoidal waveform defining a radial amplitude and a half wavelength, and the radial amplitude ranges from 5 mm to 10 mm and half wavelength ranges from 10 mm to 160 mm.
 13. The undercarriage of claim 1 wherein the plurality of track links includes a rail portion that is configured to complimentarily mate with the circumferentially undulating perimeter of the first outside portion of the idler wheel.
 14. The undercarriage of claim 13 wherein each one of the plurality of track links includes a rail portion comprising an undulating surface that is configured to complimentarily mate with the circumferentially undulating perimeter of idler wheel.
 15. The undercarriage of claim 1 wherein the undulating circumferential perimeter is uninterrupted along the circumferential direction of the idler wheel.
 16. The undercarriage of claim 1 wherein the idler wheel further includes a hub portion.
 17. The undercarriage of claim 1 wherein each one of the plurality of track links includes a rail and the idler wheel further comprises a flange that is positioned closely to the axially outside portion of the rail, being configured to help prevent axial movement of the track chain assembly with respect to the idler wheel.
 18. A machine comprising: an undercarriage including a track chain including a plurality of track pins and track bushings disposed about the track pins; and a plurality of track links that are connected to each other by either one of the plurality of track pins or a track bushings, wherein at least one of the plurality of track links defines a plurality of apertures for receiving one of the plurality of track pins or bushings; and an idler wheel including a main body that includes a generally cylindrical configuration defining an axis of rotation, a circumferential direction and a radial direction, the main body including a central portion disposed along the axis of rotation defining a radial extremity of the central portion; and at least a first outside portion disposed along the axis of rotation that includes an undulating circumferential perimeter including a plurality of apexes and valleys, wherein the undulating circumferential perimeter is exposed and configured to contact the plurality of track links of the track chain tangentially.
 19. The machine of claim 18 wherein the plurality of track links includes a plurality of offset links.
 20. The machine of claim 18 further comprising a drive sprocket that is elevated vertically above the idler wheel. 